Significance of Ripple Factor

• The output of the single phase rectifier is not pure DC but it also contains some AC components. 
• The AC component is called as ripple. The ripple factor indicates magnitude of AC component in the output. 
• Higher value of ripple factor means higher AC component in the output of the rectifier.

Ripple Factor

• It is defined as the ratio of RMS value of AC component to the DC component in the rectifier output.

       Ripple factor = RMS value of AC component / DC component

• Smaller value of ripple factor means effective rectification

Equation of Ripple Factor

The effective value of output current is given by

I_RMS =  √ ( I_DC² + I_AC² ) …….( 1 )

 I_AC = √ ( I_RMS² –  I_DC² )  ……( 2 )

Dividing equation ( 2 ) by I_DC

( I_AC / I_DC   ) = √ ( I_RMS² –  I_DC² ) / I_DC²

 Ripple Factor  = √ ( I_RMS² / I_DC² –  1 )

Ripple Factor For Half wave rectifier

I_RMS = I_MAX / 2

I_DC = I_MAX / π

Therefore, the ripple factor for half wave rectifier is

Ripple factor = √ [ I_MAX / 2 ]² / [ I_MAX / π ]² – 1

                     = √ [ π / 2 ]² – 1

                     = 1.21

• The AC component exceeds than DC component in the output of the single phase half wave rectifier. 
• The AC component is 121% than the DC component.

Ripple Factor For Full wave rectifier

I_RMS = I_MAX / √ 2

I_DC = 2I_MAX / π

Therefore, the ripple factor for half wave rectifier is

Ripple factor = √ [ I_MAX / √ 2 ]² / [ 2I_MAX / π ]² – 1

                     = √ [ π / 2√ 2 ]² – 1

                     = 0.48

• The AC component is 48% that of DC component in the output of the single phase full wave rectifier.

Sr.No	Type of Rectifier	Ripple Factor
1	Single Phase Half Wave Rectifier	1.21
2	Single Phase Full Wave Rectifier	0.48

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